Answer: anecdote
Explanation:The passage you provided can be best described as an example of "anecdote" or "anecdotal evidence." An anecdote is a brief and often personal or fictionalized account of an event that is used to illustrate or support a larger point or idea. In this case, the ambassadors' experience of witnessing the Utopians' indifference towards wealth and their subsequent change in attitude serves as an anecdote to convey the central idea that riches are not important to Utopians.